This application is a Continuation of prior International Application PCT/JP00/08817, filed Dec. 13, 2000.
The present invention relates to a process for producing a fluorinated alkylamine represented by F(CF2)n(CH2)mNH2.
A fluorinated alkylamine compound represented by F(CF2)n(CH2)mNH2 is a compound useful as a starting material for the synthesis of various organic compounds. Particularly, CF3CH2NH2 is a compound which is important as e.g. an intermediate for the synthesis of pharmaceuticals and agricultural chemicals.
As a method for producing F(CF2)n(CH2)mNH2 by reacting F(CF2)N(CH2)mX with NH3, (1) a method for producing CF3CH2NH2 by reacting from 1 to 3 times by mol of NH3 to CF3CH2X in the presence of an inert solvent such as anhydrous N-methylpyrrolidone or anhydrous glycol (U.S. Pat. No. 4,618,718), (2) a method for producing CF3CH2NH2 by reacting CF3CH2Cl with concentrated aqueous ammonia, wherein from 1 to 3 times by mol of NH3 is used relative to CF3CH2Cl (U.S. Pat. No. 2,348,321) or (3) a method for producing CF3CH2NH2 by reacting CF3CH2Cl or CF3CH2Br with concentrated aqueous ammonia, wherein 6.5 times by mol of NH3 is used relative to CF2CH2Cl or CF3CH2Br (Dickey et al, Ind. Eng. Chem., Vol. 48,209, 1956), is, for example, known.
However, in the method (1), the reaction is carried out under an industrially disadvantageous high reaction pressure (7 to 11 MPa), and it is disclosed that if the pressure is lowered, the yield of CF3CH2NH2 decreases. Further, when a duplicate test was carried out in accordance with the method (1), a problem was observed such that a part of CF3CH2NH2 was reacted with HX formed as a by-product, to form a halogenated salt (CF3CH2NH2xe2x80xa2HX), whereby the yield of CF3CH2NH2 decreased (to a level of from 70 to 87%). Further, in order to convert the formed CF3CH2NH2xe2x80xa2HX to CF3CH2NH2 for recovery, it is necessary to add an aqueous alkali solution and to carry out extraction with an organic solvent, followed by distillation for purification, thus leading to a problem that the number of process steps increases, and the process becomes cumbersome. Further, there has been an additional problem that part of the formed CF3CH2NH2 reacts with CF3CH2X to from a secondary amine compound represented by (CF3CH2)2NH or a tertiary amine compound represented by (CF3CH2)3N, whereby the yield of CF3CH2NH2 tends to be low.
Further, in the method (2) or (3), no organic solvent is employed, and concentrated aqueous ammonia is used as a reaction solvent. CF3CH2X is hardly soluble in concentrated aqueous ammonia, whereby the reactivity with NH3 tends to be low, and a problem that the yield tends to be low, was observed. Further, when the method (2) or (3) was practically employed, it was necessary to use an expensive reactor made of a corrosion resistant material such as hastelloy, since there was a problem of corrosion of the reactor.
The present invention has been made to solve the above problems and provides a process for producing a fluorinated alkylamine compound, which comprises reacting a compound represented by F(CF2)n(CH2)mX (wherein X represents a chlorine atom, a bromine atom or an iodine atom, and n and m each independently represents an integer of at least 1) with NH3 to produce a compound represented by F(CF2)n(CH2)mNH2 (wherein n and m have the same meanings as the above), and is characterized by conducting the reaction in the presence of a reaction solvent comprising an alkanediol as an essential component.
In F(CF2)n(CH2)mX in the present invention, X is preferably a chlorine atom from the viewpoint of the availability, the reactivity, etc. Further, n is preferably from 1 to 16, more preferably from 1 to 8, particularly preferably 1. m is preferably from 1 to 10, more preferably from 1 to 5, particularly preferably 1. The following compounds may be mentioned as specific examples of F(CF2)n(CH2)mX.
CF3CH2Cl, CF3CH2Br, CF3CH2I, CF3CF2CH2Cl, CF3CF2CH2Br, CF3CF2CH2 I, F(CF2)3CH2Cl, F(CF2)4CH2Cl, F(CF2)5CH2Cl, F(CF2)6CH2Cl, F(CF2)7CH2Cl, F(CF2)8CH2Cl.
CF3(CH2)2Cl, CF3(CH2)2Br, CF3(CH2)2I, CF3CF2(CH2)2Cl, CF3CF2(CH2)2Br, CF3CF2(CH2)2I, F(CF2)3(CH2)2Cl, F(CF2)4(CH2)2Cl, F(CF2)5(CH2)2Cl, F(CF2)6(CH2)2Cl, F(CF2)7(CH2)2Cl, F(CF2)8(CH2)2Cl.
CF3(CH2)3Cl, CF3(CH2)3Br, CF3(CH2)3I, CF3CF2(CH2)3Cl, CF3CF2(CH2)3Br, CF3CF2(CH2)3I, F(CF2)4(CH2)3Cl, F(CF2)4(CH2)3Cl, F(CF2)5(CH2)3Cl, F(CF2)6(CH2)3Cl, F(CF2)7(CH2)3Cl, F(C F2)8(CH2)3Cl.
In the present invention, at the time of reacting F(CF2)n(CH2)mX with NH3, a solvent comprising an alkanediol as an essential component, is used. As the alkanediol, a C2-10 alkanediol is preferred for the reason of handling efficiency and the physical properties of the solvent. Further, as such an alkanediol, octane-1,8-diol, propylene glycol or ethylene glycol is preferred. Further, propylene glycol or ethylene glycol is particularly preferred, since the effects of the present invention are thereby distinctly observed.
Further, the reaction solvent preferably consists essentially of an alkanediol or essentially of an alkanediol and water. Particularly preferred is a reaction solvent consisting essentially of at least one member selected from propylene glycol and ethylene glycol, or a reaction solvent consisting essentially of at least one member selected from propylene glycol and ethylene glycol, and water. Especially preferred is a reaction solvent consisting of at least one member selected from propylene glycol and ethylene glycol. When water is present in the solvent, the total amount of the alkanediol is preferably at least 1 mass %, more preferably at least 10 mass %, relative to water.
The alkanediol is believed to have an activity to increase the solubility of F(CF2)n(CH2)mX and the reactivity of NH3 with F(CF2)n(CH2)mX. If the proportion of the alkanediol in the reaction solvent becomes large, there will be an effect such that the yield of the fluorinated alkylamine compound will be remarkably high. Further, by using the alkanediol, F(CH2)n(CH2)mNH2 will be formed in high yield even when the reaction pressure is adjusted to be low. Further, corrosion of the reactor can be prevented by using the alkanediol.
If the amount of the reaction solvent is too much, the volume efficiency of the reactor tends to be poor, and there will be a drawback that the productivity decreases. On the other hand, if the amount of the reaction solvent is too small, NH3 and F(CF2)n(CH2)mX tend not to sufficiently be dissolved in the reaction solvent, whereby an industrially disadvantageous high reaction pressure will have to be used. Accordingly, the amount of the reaction solvent is preferably from 0.5 to 50 times by mass, more preferably from 1 to 20 times by mass, relative to F(CF2)n(CH2)mX.
In the present invention, at the time of reacting F(CF2)n(CH2)mX with NH3, it is preferred to employ at least 4 times by mol of NH3 relative to F(CF2)n(CH2)mX. Namely, HX as a by-product (HX) in the reaction of F(CF2)n(CH2)mX with NH3, will further react with NH3 to form NH4X, but if the amount of NH3 is small, HX will also react with F(CF2)n(CH2)mNH2 to form F(CF2)n(CH2)mNH2xe2x80xa2HX. However, by adjusting the amount of NH3 to be at least a certain specific level, the amount of formation of F(CF2)n(CH2)mNH2xe2x80xa2HX can be remarkably reduced. This is considered to be such that excessively present NH3 has a function to convert F(CF2)n(CH2)mNH2xe2x80xa2HX to F(CF2)n(CH2)mNH2.
On the other hand, if the amount of NH3 is too much, the reaction pressure will be high, and there will be a problem such that unreacted NH3 will remain, or the operation efficiency and economical efficiency tend to be low. From the foregoing reasons, the amount of NH3 is more preferably from 4 to 10 times by mol, particularly preferably from 4 to 6 times by mol, relative to F(CF2)n(CH2)mX.
Further, it is considered that if NH3 is present excessively, NH3 will also suppress a side reaction to form a secondary amine compound or a tertiary amine compound. Further, the alkanediol to be used as the reaction solvent, is considered to suppress such a side reaction by promoting the reaction of F(CF2)n(CH2)mX with NH3.
In the reaction of the present invention, the reaction temperature is preferably from 30 to 250xc2x0 C., more preferably from 150 to 250xc2x0 C., particularly preferably from 170 to 210xc2x0 C. The reaction temperature may not necessarily be constant and may preferably be changed as the case requires.
Further, it is preferred that the reaction pressure is suitably changed by adjusting the supply ratio of the reaction solvent and F(CF2)n(CH2)mX. Usually, it is preferably from 0.5 to 10 MPa (gauge pressure, hereinafter represented by a gauge pressure, unless otherwise specified), more preferably from 0.5 to 5 MPa, particularly preferably from 1 to 5 MPa, most preferably from 1 to 3 MPa. If the amount of the reaction solvent is large, the reaction pressure decreases, and if it is small, the reaction pressure increases. Further, if the reaction pressure is too high, such is disadvantageous from the viewpoint of the operation efficiency and capital investment, and if it is too low, no adequate reaction rate tends to be obtained. In the present invention, the product can be obtained in good yield even under low pressure, by using the alkanediol as the solvent
By the reaction of the present invention, a fluorinated alkylamine compound represented by F(CF2)n(CH2)mNH2 is formed. In the compound, n and m are the same as n and m in the starting material. The following compounds may be mentioned as specific examples of the fluorinated alkylamine compound.
CF3CH2NH2, CF3CF2CH2NH2, F(CF2)3CH2NH2, F(CF2)4CH2NH2, F(CF2)5CH2NH2, F(CF2)6CH2NH2, F(CF2)7CH2NH2, F(CF2)8CH2NH2.
CF3(CH2)2NH2, CF3CF2(CH2)2NH2, F(CF2)3(CH2)2NH2, F(CF2)4(CH2)2NH2, F(CF2)5(CH2)2NH2, F(CF2)6(CH2)2NH2, F(CF2)7(CH2)2NH2, F(CF2)8(CH2)2NH2.
CF3(CH2)3NH2, CF3CF2(CH2)3NH2, F(CF2)3(CH2)3NH2, F(CF2)4(CH2)3NH2, F(CF2)5(CH2)3NH2, F(CF2)6(CH2)3NH2, F(CF2)7(CH2)3NH2, F(CF2)8(CH2)3NH2.
The reaction of the present invention is carried out preferably by introducing the reaction solvent, F(CF2)n(CH2)mX and NH3 into a reactor by a batch system or a continuous system and dissolving the compounds in the reaction system in the reaction solvent. The timing for introducing NH3 and F(CF2)n(CH2)mX is not particularly limited, and a method of charging all the amounts all at once preliminarily before the reaction, a method of continuously supplying them during the reaction, or a method of dividedly supplying them during the reaction, may, for example, be mentioned.
Further, at the initial stage of the reaction, the reaction may be carried out by a small amount of NH3, and at the final stage of the reaction, the reaction may be carried out by supplying a large amount of NH3. Here, if the amount of NH3 used at the initial stage of the reaction is small, (CF2)n(CH2)mNH2xe2x80xa2HX may be formed, but even in such a case, by supplying NH3 in a large amount at the final stage of the reaction, it is possible to reduce the amount of formation of F(CF2)n(CH2)mNH2xe2x80xa2HX and increase the yield of the desired compound.
In the reaction of the present invention, the conversion and selectivity are high, whereby a reaction crude product containing the fluorinated alkylamine compound obtained by the reaction can be made to be a fluorinated alkylamine compound of high purity by a simple purification operation. For example, by subjecting the reaction crude product to purification by distillation as it is, it is possible to recover F(CF2)n(CH2)mNH2 of high purity. At the time of the distillation, it is preferred to maintain the condenser temperature to a level lower by at least 10xc2x0 C. than the boiling point of F(CF2)n(CH2)mNH2 in order to prevent a decrease in the recovery rate by discharge of F(CF2)n(CH2)mNH2 together with NH3. Further, the pressure during the distillation is preferably adjusted to be at least 0.1 MPa (absolute pressure).
The fluorinated alkylamine compound is a compound useful as a starting material for the synthesis of various organic compounds. For example, CF3CH2NH2 is a compound which is important as an intermediate for the synthesis of therapeutic agents for osteoporosis, cancer, etc., or as an intermediate for the synthesis of agricultural chemicals.